Re: [heycam/webidl] undefined can't be a member of a union type (#962)

Looking over the remaining spots where `undefined` is mentioned, I'm not entirely sure what to do about the "convert an ES value to an IDL union type" part, and I think it raises questions about distinguishability too:

> If V is null or undefined, then:
> 
> * If types includes a dictionary type, then return the result of converting V to that dictionary type.

So this implies that the current behavior is that a JS `undefined` can always be converted into a dictionary type. I presume this is fallout from the fact that dictionary *arguments* are required to be optional. Does this imply that `undefined` and dictionary types should not be distinguishable, tho?  Or is it okay for them to remain distinguishable, so I'll add a new first step that checks if the union type contains `undefined`, and then the dictionary conversion is a fallback?

(Also, hm, all of the 3.2.24 algo confuses me, since it's composed of nested conditionals where the inner conditionals don't have "else" clauses. Is the implication that you continue to next top-level step if you fail all the conditions?)

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/heycam/webidl/issues/962#issuecomment-796938662